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Versions: 00

Mboned                                                        J. Holland
Internet-Draft                                                   K. Rose
Intended status: Experimental                  Akamai Technologies, Inc.
Expires: December 31, 2018                                 June 29, 2018


                  Asymmetric Manifest Based Integrity
                     draft-jholland-mboned-ambi-00

Abstract

   This document introduces Asymmetric Manifest-Based Integrity (AMBI).
   AMBI allows each receiver of a stream of multicast packets to check
   the integrity of the contents of each packet in the data stream.
   AMBI operates by passing cryptographically verifiable manifests for
   the data packets, over out-of-band communication channels.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 31, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Comparison with TESLA . . . . . . . . . . . . . . . . . .   4
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Protocol Specification  . . . . . . . . . . . . . . . . . . .   4
     2.1.  Packet Identifiers  . . . . . . . . . . . . . . . . . . .   4
       2.1.1.  Overview  . . . . . . . . . . . . . . . . . . . . . .   4
       2.1.2.  RTP Sequence Number . . . . . . . . . . . . . . . . .   5
       2.1.3.  SRTP Sequence Number  . . . . . . . . . . . . . . . .   5
       2.1.4.  UDP Option  . . . . . . . . . . . . . . . . . . . . .   5
     2.2.  Anchor Message  . . . . . . . . . . . . . . . . . . . . .   6
       2.2.1.  Overview  . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.2.  DNS-based Anchor URI Bootstrap  . . . . . . . . . . .   6
       2.2.3.  Anchor Message YANG model . . . . . . . . . . . . . .   6
       2.2.4.  Example Anchor Message  . . . . . . . . . . . . . . .  13
     2.3.  Manifests . . . . . . . . . . . . . . . . . . . . . . . .  15
       2.3.1.  Overview  . . . . . . . . . . . . . . . . . . . . . .  15
       2.3.2.  Manifest Layout . . . . . . . . . . . . . . . . . . .  15
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
     4.1.  Packet Identifiers  . . . . . . . . . . . . . . . . . . .  17
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     5.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   Multicast transport poses security problems that are not easily
   addressed by the same security mechanisms used for unicast transport.

   The "Introduction" sections of the documents describing TESLA
   [RFC4082], and TESLA in SRTP [RFC4383], and TESLA with ALC and NORM
   [RFC5776] present excellent overviews of the challenges unique to
   multicast authentication, briefly summarized here:

   o  A MAC based on a symmetric shared secret cannot be used because
      each packet has multiple receivers that do not trust each other.

   o  Asymmetric per-packet signatures can handle only very low bit-
      rates because of the computational overhead.

   o  An asymmetric signature of a larger message comprising multiple
      packets requires reliable receipt of all such packets, something
      that cannot be guaranteed in a timely manner even for protocols
      that do provide reliable delivery, and the retransmission of which




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      may anyway exceed the useful lifetime for data formats that can
      otherwise tolerate some degree of loss.

   Aymmetric Manifest-Based Integrity (AMBI) specifies a method for
   receivers or middle boxes to cryptographically authenticate and
   verify the integrity of a stream of packets, by communicating packet
   "manifests" (described in Section 2.3) via an out-of-band
   communication channel that provides authentication and verifiable
   integrity.

   Each manifest contains cryptographic hashes of packet payloads
   corresponding to specific packets in the authenticated data stream.

   Three ways to authenticate a manifest are defined:

   o  Asymmetric signature of a message containing the manifest.

   o  Authenticated unicast stream providing a sequence of manifests.

   o  Using one of the prior two constructions to bootstrap a root
      manifest containing authentication information for further
      manifests.  This we term "recursive authentication".

   When using asymmetric signatures, recursive authentication allows the
   sender to amortize the computational overhead for a single asymmetric
   signature across enough data packets to sustain high data rates.
   When using a secure unicast stream, the recursive verification allows
   for scaling the authenticated data stream to more receivers than can
   otherwise be sustained with a limited set of trusted servers.

   Upon successful verification of the contents of a manifest and
   receipt of any subset of the corresponding data packets, the receiver
   has proof of the integrity of the contents of the data packets listed
   in the manifest.

   An "anchor message", described in Section 2.2, provides the link
   between an authenticated data stream and the out-of-band channel of
   manifests that authenticates it.

   Authenticating the integrity of the data packets depends on:

   o  authentication of the anchor message that provides the linkage
      between the manifest channel and the data stream; and

   o  the secrecy and cryptographic strength of private keys used for
      signing manifests, or the authentication of the secure unicast
      streams used for transmitting manifests; and




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   o  the difficulty of generating a collision for the packet hashes in
      the manifest.

1.1.  Comparison with TESLA

   AMBI and TESLA [RFC4082] and [RFC5776] attempt to achieve a similar
   goal of authenticating the integrity of streams of multicast packets.
   AMBI imposes a higher overhead, as measured in the amount of extra
   data required, than TESLA imposes.  In exchange, AMBI provides non-
   repudiation (which TESLA does not), and relaxes the requirement for
   establishing an upper bound on clock synchronization between sender
   and receiver.

   This tradeoff enables new capabilities for AMBI, relative to TESLA.
   In particular, when receiving multicast traffic from an untrusted
   transit network, AMBI can be used by a middle box to authenticate
   packets from a trusted source before forwarding traffic through the
   network, and the receiver also can separately authenticate the
   packets.  (This use case is not possible with TESLA because the data
   packets can't be authenticated until a key is disclosed, so either
   the middlebox has to forward data packets without first
   authenticating so that the receiver has them prior to key disclosure,
   or the middlebox has to hold packets until the key is disclosed, at
   which point the receiver can no longer establish their authenticity.)

1.2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  Protocol Specification

2.1.  Packet Identifiers

2.1.1.  Overview

   Packet identifiers are a sequence number contained within the
   authenticated payload of the packet.  This sequence number is used
   inside a manifest to associate each packet hash with a specific
   packet.  Each authenticated packet MUST contain a packet identifier.
   See Section 4.1 for a discussion of the security implications.

   This document defines a new UDP option in Section 2.1.4 for use as a
   packet identifier.

   Some multicast-capable transport protocols have a sequence number
   embedded in data packets in the protocol.  The sequence numbers in



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   these protocols MAY be used instead of the new UDP option, to avoid
   introducing extra overhead in the authenticated data packets.

   In Section 2.1.2, Section 2.1.3, and Section 2.1.4, this document
   defines some sample ways to specify packet identifiers based on such
   sequence numbers embedded in existing protocols.

   Other appropriate sequence number systems may exist, such as the
   anti-replay Sequence Number field in Section 3.1 of [RFC6584], when
   NORM or FLUTE operates with an authentication profile that uses it
   (however, since that example already provides authentication, it is
   not added as an option in this document).  The AMBI anchor message
   format can be extended in future documents to support those or other
   suitable schemes by adding values to the registry defined in
   Section 3.

   In some deployments, in contrast to using the new UDP option, the
   approach of using an existing sequence number may carry a benefit
   because it requires no change to the stream of packets being
   authenticated, possibly enabling interoperability with legacy
   receivers.

2.1.2.  RTP Sequence Number

   Sequence number from Section 5.1 of [RFC3550].

   TBD: discussion of security consequences of using 16 bits- recommend
   a bigger hash in manifests for this case?

2.1.3.  SRTP Sequence Number

   Packet Index from Section 3.3.1 of [RFC3711].

2.1.4.  UDP Option

   Define a new UDP option [I-D.ietf-tsvwg-udp-options] (TBD2).

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | UDP Kind=TBD2 |    Length=6   |      32-bit sequence number   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+







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2.2.  Anchor Message

2.2.1.  Overview

   An anchor message provides the information that makes it possible to
   associate the manifests with the data packets they authenticate.  ID
   values that appear as text integers in the anchor message also appear
   in the manifest binary data, with the anchor message providing
   context on how to interpret the values.

   An anchor message MAY be discovered and transmitted by any means
   which provides adequate source authentication and data integrity to
   meet the security needs of the receiver.

   In order to support middle-box authentication, it is RECOMMENDED that
   senders arrange to distribute anchor messages according to the method
   outlined in Section 2.2.2.

2.2.2.  DNS-based Anchor URI Bootstrap

   When a middle box tries to process a join for a specific source, if
   it is configured to perform authentication on SSM multicast channels
   it can forward, it SHOULD make a DNS request for ambi.(reverse-
   source-ip).ip6.arpa or ambi.(reverse-source-ip).in-addr.arpa, for
   IPv6 or IPv4 source addresses.

   When AMBI is provided to authenticate traffic from this source IP,
   this domain name SHOULD be configured with a TXT field which contains
   a URI that can be used to securely fetch an anchor message that
   describes all the AMBI- authenticatable traffic from this source IP.

   Other methods MAY be used to discover and transfer an anchor message.
   The description of alternate methods is out of scope for this
   document.

   TBD: consider breaking up anchor message to avoid large, frequently
   changing anchors for sources with many groups.

   TBD: consider graceful rollover for anchors, instead of synchronized
   update of anchor hash.

2.2.3.  Anchor Message YANG model

<CODE BEGINS> file "ietf-ambi-anchor.yang"
module ietf-ambi-anchor {
    yang-version 1.1;

    namespace "urn:ietf:params:xml:ns:yang:ietf-ambi-anchor";



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    prefix "ambi";

    import ietf-yang-types {
        prefix "yang";
        reference "RFC6991 Section 3";
    }

    import ietf-inet-types {
        prefix "inet";
        reference "RFC6991 Section 4";
    }

    import ietf-routing-types {
        prefix "rt-types";
        reference "RFC8294";
    }

    organization "IETF";

    contact
        "Author:   Jake Holland
                   <mailto:jholland@akamai.com>
         Author:   Kyle Rose
                   <mailto:krose@akamai.com>
        ";

    description
        "This module contains the definition for the AMBI anchor
         message data type.

         Copyright (c) 2018 IETF Trust and the persons identified as
         authors of the code.  All rights reserved.

         Redistribution and use in source and binary forms, with or
         without modification, is permitted pursuant to, and subject
         to the license terms contained in, the Simplified BSD License
         set forth in Section 4.c of the IETF Trust's Legal Provisions
         Relating to IETF Documents
         (http://trustee.ietf.org/license-info).

         This version of this YANG module is part of
         draft-jholland-mboned-ambi,
         see the internet draft itself for full legal notices.";

    revision 2018-06-27 {
        description "Initial revision.";
        reference
          "";



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    }

    /* TBD: copied some from https://tools.ietf.org/html/rfc8177,
       but the model doesn't seem to match what I want. is there another
       I can import instead of making these here? Or a registry
       to reference? */
    identity crypto-hash {
        description
            "Base identity of cryptographic hash options. ";
    }

    identity sha-256 {
        base crypto-hash;
        description
            "The SHA-256 algorithm.";
    }

    identity blake2b {
        base crypto-hash;
        description
            "The BLAKE2b algorithm.";
    }

    identity crypto-signature {
        description
            "Base identity of cryptographic asymmetric signature
             options.";
    }

    identity ed25519 {
        base crypto-signature;
        description
            "The Ed25519 algorithm.";
    }

    identity rsa {
        base crypto-signature;
        description
            "The RSA algorithm.";
    }

    identity sequence-type {
        description
            "Base identity for sequence number type options.";
    }

    identity rtp {
        base sequence-type;



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        description
            "The sequence number from RTP.";
    }

    identity srtp {
        base sequence-type;
        description
            "The sequence number from SRTP.";
    }

    identity udp {
        base sequence-type;
        description
            "The sequence number from UDP.";
    }
    typedef key-identifier {
        type uint16 {
            range 1..65535;
        }
        description "Key identifier within a manifest";
    }

    typedef bitrate {
        type string {
          pattern '[1-9][0-9]*[GMK]?bps';
        }
        description "Bit-rate of a data stream";
    }

    typedef packetrate {
        type string {
          pattern '[1-9][0-9]*[GMK]?pps';
        }
        description "Packet rate of a data stream";
    }

    typedef manifest-transport {
        type union {
            type leafref {
                path "/anchor/data_stream/id";
            }
            type inet:uri;
        }
        description "Transport method for a manifest stream";
    }

    container anchor {
        container self {



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            presence "An anchor message exists";
            description
                "Self-referential properties about the anchor message";
            leaf uri {
                type inet:uri;
                mandatory true;
                description
                    "The canonical URI for this anchor message.";
            }
            leaf version {
                type uint16;
                mandatory true;
                description
                    "The version number for this anchor message.";
            }
            leaf hash_algorithm {
                type identityref {
                    base crypto-hash;
                }
                mandatory true;
                description
                    "The algorithm for the anchor message hash provided
                     in a manifest.";
            }
            leaf hash_bits {
                type uint16;
                mandatory true;
                description
                    "The number of bits for the anchor's hash provided
                     in a manifest.";
            }
            leaf expires {
                type yang:date-and-time;
                mandatory true;
                description
                    "The expiration time for this anchor message.";
            }
        }
        description "Anchor message for AMBI";

        list public_key {
            key id;
            description "Public key for non-recursive manifest";
            leaf id {
                type key-identifier;
                mandatory true;
                description
                    "The key identifier referenced in a manifest.";



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            }
            leaf algorithm {
                type identityref {
                    base crypto-signature;
                }
                mandatory true;
                description
                    "The signature algorithm for use with this key.";
            }
            leaf signature_bits {
                type uint16;
                mandatory true;
                description
                    "The length of the signature provided in manifests
                     signed with this key.";
            }
            leaf value {
                type string;
                mandatory true;
                description
                    "The base64-encoded value of the public key.";
            }
        }

        list data_stream {
            key id;
            unique "source destination port";
            description "Stream of data packets to be authenticated";
            leaf id {
                type uint16;
                mandatory true;
                description
                    "The datastream_id referenced by a
                     manifest_stream.";
            }
            leaf source {
                type inet:ip-address;
                mandatory true;
                description
                    "The source IP address of the authenticated data
                     stream.";
            }
            leaf destination {
                type rt-types:ip-multicast-group-address;
                mandatory true;
                description
                    "The destination group IP address of the
                     authenticated data stream.";



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            }
            leaf port {
                type uint16;
                mandatory true;
                description
                    "The destination UDP port of the authenticated data
                     stream.";
            }
            leaf max_bitrate {
                type bitrate;
                mandatory true;
                description
                    "The maximum bitrate expected for this data
                     stream.";
            }
            leaf max_packetrate {
                type packetrate;
                mandatory true;
                description
                    "The maximum packetrate expected for this data
                     stream.";
            }
            list authenticator {
                key manifest_id;
                description
                    "A manifest stream that authenticates this data";
                leaf manifest_id {
                    type leafref {
                        path "/anchor/manifest_stream/id";
                    }
                    mandatory true;
                    description
                        "The ID of a manifest stream that provides
                         authentication for this data stream.";
                }
            }
        }

        list manifest_stream {
            key id;
            description "Stream of manifests";
            leaf id {
                type uint16;
                mandatory true;
                description "The Manifest ID referenced in a manifest.";
            }
            leaf transport {
                type manifest-transport;



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                mandatory true;
                description
                    "The ID of the data stream that carries this
                     manifest stream or a uri that provides a websocket
                     with the stream of manifests.";
            }
            leaf hash_algorithm {
                type identityref {
                    base crypto-hash;
                }
                mandatory true;
                description
                    "The hash algorithm for the packet hashes within
                     manifests in this stream.";
            }
            leaf hash_bits {
                type uint16;
                mandatory true;
                description
                    "The number of bits of hash provided for packet
                     hashes.";
            }
            leaf sequence_type {
                type identityref {
                    base sequence-type;
                }
                mandatory true;
                description
                    "The linkage to the data packet sequence numbers in
                     the manifest.";
            }
        }
    }
}
<CODE ENDS>

                    Figure 1: Anchor Message YANG model

2.2.4.  Example Anchor Message

   {
     "ietf-ambi-anchor:anchor": {
       "self": {
         "uri": "https://example.com/ambi/anchor/example_1.json",
         "version": 1,
         "hash_algorithm": "blake2b",
         "hash_bits": 256,
         "expires": "2018-03-05T23:59:59Z"



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       },
       "public_key": [
         {
           "id": 1,
           "algorithm": "ed25519",
           "signature_bits": 256,
           "value": "VGhpcyBpcyBub3QgYSBnb29kIGtleSB0byB1c2UuLi4NCg=="
         }
       ],
       "data_stream": [
         {
           "id": 10,
           "source": "192.0.2.10",
           "destination": "232.10.10.1",
           "port": 18001,
           "max_bitrate": "10Mbps",
           "max_packetrate": "1Kpps",
           "authenticator": [
             {
               "manifest_id": 1
             }
           ]
         },
         {
           "id": 20,
           "source": "192.0.2.10",
           "destination": "232.10.10.1",
           "port": 18002,
           "max_bitrate": "400Kbps",
           "max_packetrate": "40pps",
           "authenticator": [
             {
               "manifest_id": 2
             }
           ]
         }
       ],
       "manifest_stream": [
         {
           "id": 1,
           "transport": 20,
           "hash_algorithm": "blake2b",
           "hash_bits": 80,
           "sequence_type": "udp"
         },
         {
           "id": 2,
           "transport": "https://example.com/ambi/manifest_stream/3",



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           "hash_algorithm": "blake2b",
           "hash_bits": 80,
           "sequence_type": "udp"
         }
       ]
     }
   }

                     Figure 2: Example Anchor Message

2.3.  Manifests

2.3.1.  Overview

   A manifest cannot be interpreted except in context of a known anchor
   message.  In order for a manifest to be considered as potentially
   authenticating a set of packets, the anchor version MUST match the
   value in a known unexpired anchor message, and the hash MUST match
   the hash of the contents of that anchor message, according to the
   /anchor/self/hash_algorithm and /anchor/self/hash_bits fields, in
   order for a manifest to be accepted for use as evidence of
   authenticity and integrity.

2.3.2.  Manifest Layout



























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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Ver=0 |     Reserved=0      |S|       Anchor Version          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Anchor Hash (variable length, 4-byte aligned, 0-padded)    |
   |                             ...                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Key ID             |         Manifest ID           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               First Packet Hash Identifier                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Packet Identifier Step (if S-bit set)             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Packet Hash Count       |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   |            Cryptographic Signature (if Key ID nonzero)        |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                      ... Packet Hashes ...                    |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.  IANA Considerations

   TBD1: Request a "Specification Required" registry for Packet
   identifier methods, from https://tools.ietf.org/html/rfc5226#section-
   4.1 . Reserve anything beginning with "experimental:"?

   TBD2: Add a new entry to the "UDP Option Kind" numbers registry:
   https://tools.ietf.org/html/draft-ietf-tsvwg-udp-options-
   02#section-14

   TBD: check guidelines in https://tools.ietf.org/html/rfc5226 and
   remove this paragraph

   Example from: https://tools.ietf.org/html/rfc5226#section-5.1

   [TO BE REMOVED: Please add the yang model in Section 2.2.3 to:
   https://www.iana.org/assignments/yang-parameters/yang-
   parameters.xhtml

   Name:ietf-ambi-anchor Maintained by IANA: N Namespace:
   urn:ietf:params:xml:ns:yang:ietf-ambi-anchor Prefix: anchor
   Reference: I-D.draft-jholland-mboned-ambi Notes: ]




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4.  Security Considerations

4.1.  Packet Identifiers

   TBD: explain attack from generating malicious packets and then
   looking for collisions, as opposed to having to generate a collision
   including a sequence number and then hitting a match

   TBD: DNSSEC vis-a-vis anchor url discovery.  (we need a diagram about
   for middle-box handling of a revers-path propagated join?)  Explain
   why malicious DNS could deny service, but cannot cause accepting
   attack packets.

   TBD: follow the rest of the guidelines: https://tools.ietf.org/html/
   rfc3552

5.  References

5.1.  Normative References

   [I-D.ietf-tsvwg-udp-options]
              Touch, J., "Transport Options for UDP", draft-ietf-tsvwg-
              udp-options-02 (work in progress), January 2018.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              July 2003, <https://www.rfc-editor.org/info/rfc3550>.

   [RFC3711]  Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
              Norrman, "The Secure Real-time Transport Protocol (SRTP)",
              RFC 3711, DOI 10.17487/RFC3711, March 2004,
              <https://www.rfc-editor.org/info/rfc3711>.

5.2.  Informative References

   [DIGSIGN]  Rohatgi, P., "How to Sign Digital Streams", 1997,
              <https://link.springer.com/content/pdf/10.1007/
              BFb0052235.pdf>.

              Published in CRYPTO '97 "Proceedings of the 17th Annual
              International Cryptology Conference on Advances in
              Cryptology", Pages 180-197



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Internet-Draft                    AMBI                         June 2018


   [RFC4082]  Perrig, A., Song, D., Canetti, R., Tygar, J., and B.
              Briscoe, "Timed Efficient Stream Loss-Tolerant
              Authentication (TESLA): Multicast Source Authentication
              Transform Introduction", RFC 4082, DOI 10.17487/RFC4082,
              June 2005, <https://www.rfc-editor.org/info/rfc4082>.

   [RFC4383]  Baugher, M. and E. Carrara, "The Use of Timed Efficient
              Stream Loss-Tolerant Authentication (TESLA) in the Secure
              Real-time Transport Protocol (SRTP)", RFC 4383,
              DOI 10.17487/RFC4383, February 2006,
              <https://www.rfc-editor.org/info/rfc4383>.

   [RFC5776]  Roca, V., Francillon, A., and S. Faurite, "Use of Timed
              Efficient Stream Loss-Tolerant Authentication (TESLA) in
              the Asynchronous Layered Coding (ALC) and NACK-Oriented
              Reliable Multicast (NORM) Protocols", RFC 5776,
              DOI 10.17487/RFC5776, April 2010,
              <https://www.rfc-editor.org/info/rfc5776>.

   [RFC6584]  Roca, V., "Simple Authentication Schemes for the
              Asynchronous Layered Coding (ALC) and NACK-Oriented
              Reliable Multicast (NORM) Protocols", RFC 6584,
              DOI 10.17487/RFC6584, April 2012,
              <https://www.rfc-editor.org/info/rfc6584>.

Authors' Addresses

   Jake Holland
   Akamai Technologies, Inc.
   150 Broadway
   Cambridge, MA 02144
   United States of America

   Email: jakeholland.net@gmail.com


   Kyle Rose
   Akamai Technologies, Inc.
   150 Broadway
   Cambridge, MA 02144
   United States of America

   Email: krose@krose.org








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